> absolutely rite Mohammad>>> On Sat, May 11, 2013 at 9:33 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>> Sorry for barging in guys. I think Nitin is talking about this :>>>> Every file and block in HDFS is treated as an object and for each object>> around 200B of metadata get created. So the NN should be powerful enough to>> handle that much metadata, since it is going to be in-memory. Actually>> memory is the most important metric when it comes to NN.>>>> Am I correct @Nitin?>>>> @Thoihen : As Nitin has said, when you talk about that much data you>> don't actually just do a "put". You could use something like "distcp" for>> parallel copying. A better approach would be to use a data aggregation tool>> like Flume or Chukwa, as Nitin has already pointed. Facebook uses their own>> data aggregation tool, called Scribe for this purpose.>>>> Warm Regards,>> Tariq>> cloudfront.blogspot.com>>>>>> On Sat, May 11, 2013 at 9:20 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:>>>>> NN would still be in picture because it will be writing a lot of meta>>> data for each individual file. so you will need a NN capable enough which>>> can store the metadata for your entire dataset. Data will never go to NN>>> but lot of metadata about data will be on NN so its always good idea to>>> have a strong NN.>>>>>>>>> On Sat, May 11, 2013 at 9:11 PM, Rahul Bhattacharjee <>>> [EMAIL PROTECTED]> wrote:>>>>>>> @Nitin , parallel dfs to write to hdfs is great , but could not>>>> understand the meaning of capable NN. As I know , the NN would not be a>>>> part of the actual data write pipeline , means that the data would not>>>> travel through the NN , the dfs would contact the NN from time to time to>>>> get locations of DN as where to store the data blocks.>>>>>>>> Thanks,>>>> Rahul>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 4:54 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:>>>>>>>>> is it safe? .. there is no direct answer yes or no>>>>>>>>>> when you say , you have files worth 10TB files and you want to upload>>>>> to HDFS, several factors come into picture>>>>>>>>>> 1) Is the machine in the same network as your hadoop cluster?>>>>> 2) If there guarantee that network will not go down?>>>>>>>>>> and Most importantly I assume that you have a capable hadoop cluster.>>>>> By that I mean you have a capable namenode.>>>>>>>>>> I would definitely not write files sequentially in HDFS. I would>>>>> prefer to write files in parallel to hdfs to utilize the DFS write features>>>>> to speed up the process.>>>>> you can hdfs put command in parallel manner and in my experience it>>>>> has not failed when we write a lot of data.>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 4:38 PM, maisnam ns <[EMAIL PROTECTED]>wrote:>>>>>>>>>>> @Nitin Pawar , thanks for clearing my doubts .>>>>>>>>>>>> But I have one more question , say I have 10 TB data in the pipeline .>>>>>>>>>>>> Is it perfectly OK to use hadopo fs put command to upload these files>>>>>> of size 10 TB and is there any limit to the file size using hadoop command>>>>>> line . Can hadoop put command line work with huge data.>>>>>>>>>>>> Thanks in advance>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 4:24 PM, Nitin Pawar <[EMAIL PROTECTED]>>>>>> > wrote:>>>>>>>>>>>>> first of all .. most of the companies do not get 100 PB of data in>>>>>>> one go. Its an accumulating process and most of the companies do have a>>>>>>> data pipeline in place where the data is written to hdfs on a frequency>>>>>>> basis and then its retained on hdfs for some duration as per needed and>>>>>>> from there its sent to archivers or deleted.

Can anyone help me know how does companies like Facebook ,Yahoo etc uploadbulk files say to the tune of 100 petabytes to Hadoop HDFS cluster forprocessingand after processing how they download those files from HDFS to local filesystem.

I don't think they might be using the command line hadoop fs put to uploadfiles as it would take too long or do they divide say 10 parts each 10petabytes and compress and use the command line hadoop fs put

first of all .. most of the companies do not get 100 PB of data in one go.Its an accumulating process and most of the companies do have a datapipeline in place where the data is written to hdfs on a frequency basisand then its retained on hdfs for some duration as per needed and fromthere its sent to archivers or deleted.

For data management products, you can look at falcon which is open sourcedby inmobi along with hortonworks.

In any case, if you want to write files to hdfs there are few optionsavailable to you1) Write your dfs client which writes to dfs2) use hdfs proxy3) there is webhdfs4) command line hdfs5) data collection tools come with support to write to hdfs like flume etcOn Sat, May 11, 2013 at 4:19 PM, Thoihen Maibam <[EMAIL PROTECTED]>wrote:

> Hi All,>> Can anyone help me know how does companies like Facebook ,Yahoo etc upload> bulk files say to the tune of 100 petabytes to Hadoop HDFS cluster for> processing> and after processing how they download those files from HDFS to local file> system.>> I don't think they might be using the command line hadoop fs put to upload> files as it would take too long or do they divide say 10 parts each 10> petabytes and compress and use the command line hadoop fs put>> Or if they use any tool to upload huge files.>> Please help me .>> Thanks> thoihen>

> first of all .. most of the companies do not get 100 PB of data in one go.> Its an accumulating process and most of the companies do have a data> pipeline in place where the data is written to hdfs on a frequency basis> and then its retained on hdfs for some duration as per needed and from> there its sent to archivers or deleted.>> For data management products, you can look at falcon which is open sourced> by inmobi along with hortonworks.>> In any case, if you want to write files to hdfs there are few options> available to you> 1) Write your dfs client which writes to dfs> 2) use hdfs proxy> 3) there is webhdfs> 4) command line hdfs> 5) data collection tools come with support to write to hdfs like flume etc>>> On Sat, May 11, 2013 at 4:19 PM, Thoihen Maibam <[EMAIL PROTECTED]>wrote:>>> Hi All,>>>> Can anyone help me know how does companies like Facebook ,Yahoo etc>> upload bulk files say to the tune of 100 petabytes to Hadoop HDFS cluster>> for processing>> and after processing how they download those files from HDFS to local>> file system.>>>> I don't think they might be using the command line hadoop fs put to>> upload files as it would take too long or do they divide say 10 parts each>> 10 petabytes and compress and use the command line hadoop fs put>>>> Or if they use any tool to upload huge files.>>>> Please help me .>>>> Thanks>> thoihen>>>>>> --> Nitin Pawar>

when you say , you have files worth 10TB files and you want to upload toHDFS, several factors come into picture

1) Is the machine in the same network as your hadoop cluster?2) If there guarantee that network will not go down?

and Most importantly I assume that you have a capable hadoop cluster. Bythat I mean you have a capable namenode.

I would definitely not write files sequentially in HDFS. I would prefer towrite files in parallel to hdfs to utilize the DFS write features to speedup the process.you can hdfs put command in parallel manner and in my experience it has notfailed when we write a lot of data.On Sat, May 11, 2013 at 4:38 PM, maisnam ns <[EMAIL PROTECTED]> wrote:

> @Nitin Pawar , thanks for clearing my doubts .>> But I have one more question , say I have 10 TB data in the pipeline .>> Is it perfectly OK to use hadopo fs put command to upload these files of> size 10 TB and is there any limit to the file size using hadoop command> line . Can hadoop put command line work with huge data.>> Thanks in advance>>> On Sat, May 11, 2013 at 4:24 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:>>> first of all .. most of the companies do not get 100 PB of data in one>> go. Its an accumulating process and most of the companies do have a data>> pipeline in place where the data is written to hdfs on a frequency basis>> and then its retained on hdfs for some duration as per needed and from>> there its sent to archivers or deleted.>>>> For data management products, you can look at falcon which is open>> sourced by inmobi along with hortonworks.>>>> In any case, if you want to write files to hdfs there are few options>> available to you>> 1) Write your dfs client which writes to dfs>> 2) use hdfs proxy>> 3) there is webhdfs>> 4) command line hdfs>> 5) data collection tools come with support to write to hdfs like flume etc>>>>>> On Sat, May 11, 2013 at 4:19 PM, Thoihen Maibam <[EMAIL PROTECTED]>wrote:>>>>> Hi All,>>>>>> Can anyone help me know how does companies like Facebook ,Yahoo etc>>> upload bulk files say to the tune of 100 petabytes to Hadoop HDFS cluster>>> for processing>>> and after processing how they download those files from HDFS to local>>> file system.>>>>>> I don't think they might be using the command line hadoop fs put to>>> upload files as it would take too long or do they divide say 10 parts each>>> 10 petabytes and compress and use the command line hadoop fs put>>>>>> Or if they use any tool to upload huge files.>>>>>> Please help me .>>>>>> Thanks>>> thoihen>>>>>>>>>>> -->> Nitin Pawar>>>>-- Nitin Pawar

The number of maps is decided as follows. Since it’s a good idea to geteach map to copy a reasonable amount of data to minimize overheads in tasksetup, each map copies at least 256 MB (unless the total size of the inputis less, in which case one map handles it all). For example, 1 GB of fileswill be given four map tasks. When the data size is very large, it becomesnecessary to limit the number of maps in order to limit bandwidth andcluster utilization. By default, the maximum number of maps is 20 per(tasktracker) cluster node. For example, copying 1,000 GB of files to a100-node cluster will allocate 2,000 maps (20 per node), so each will copy512 MB on average. This can be reduced by specifying the-m argument to *distcp*. For example, -m 1000 would allocate 1,000 maps, each copying 1 GBon average.

> Soon after replying I realized something else related to this.>> Say we have a single file in HDFS (hdfs configured for default block size> 64 MB) and the size of the file is 1 GB. Now if we use distcp to move it> from the current hdfs to another one , then> whether there would be any parallelism or just a single map task would be> fired?>> As per what I have read , a mapper is launcher for a complete file or a> set of files. It doesn't operate at block level.So no parallelism even if> the file resides in HDFS.>> Thanks,> Rahul>>> On Sun, May 12, 2013 at 6:28 PM, Rahul Bhattacharjee <> [EMAIL PROTECTED]> wrote:>>> yeah you are right I mis read your earlier post.>>>> Thanks,>> Rahul>>>>>> On Sun, May 12, 2013 at 6:25 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>> I had said that if you use distcp to copy data *from localFS to HDFS*then you won't be able to exploit parallelism as entire file is present on>>> a single machine. So no multiple TTs.>>>>>> Please comment if you think I am wring somewhere.>>>>>> Warm Regards,>>> Tariq>>> cloudfront.blogspot.com>>>>>>>>> On Sun, May 12, 2013 at 6:15 PM, Rahul Bhattacharjee <>>> [EMAIL PROTECTED]> wrote:>>>>>>> Yes , it's a MR job under the hood . my question was that you wrote>>>> that using distcp you loose the benefits of parallel processing of Hadoop.>>>> I think the MR job of distcp divides files into individual map tasks based>>>> on the total size of the transfer , so multiple mappers would still be>>>> spawned if the size of transfer is huge and they would work in parallel.>>>>>>>> Correct me if there is anything wrong!>>>>>>>> Thanks,>>>> Rahul>>>>>>>>>>>> On Sun, May 12, 2013 at 6:07 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>>>> No. distcp is actually a mapreduce job under the hood.>>>>>>>>>> Warm Regards,>>>>> Tariq>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>> On Sun, May 12, 2013 at 6:00 PM, Rahul Bhattacharjee <>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>> Thanks to both of you!>>>>>>>>>>>> Rahul>>>>>>>>>>>>>>>>>> On Sun, May 12, 2013 at 5:36 PM, Nitin Pawar <[EMAIL PROTECTED]>>>>>> > wrote:>>>>>>>>>>>>> you can do that using file:///>>>>>>>>>>>>>> example:>>>>>>>>>>>>>>>>>>>>>>>>>>>> hadoop distcp hdfs://localhost:8020/somefile file:///Users/myhome/Desktop/>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sun, May 12, 2013 at 5:23 PM, Rahul Bhattacharjee <>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>> @Tariq can you point me to some resource which shows how distcp is>>>>>>>> used to upload files from local to hdfs.>>>>>>>>>>>>>>>> isn't distcp a MR job ? wouldn't it need the data to be already>>>>>>>> present in the hadoop's fs?>>>>>>>>>>>>>>>> Rahul>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:52 PM, Mohammad Tariq <>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>

> You'r welcome :)>> Warm Regards,> Tariq> cloudfront.blogspot.com>>> On Sat, May 11, 2013 at 10:46 PM, Rahul Bhattacharjee <> [EMAIL PROTECTED]> wrote:>>> Thanks Tariq!>>>>>> On Sat, May 11, 2013 at 10:34 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>> @Rahul : Yes. distcp can do that.>>>>>> And, bigger the files lesser the metadata hence lesser memory>>> consumption.>>>>>> Warm Regards,>>> Tariq>>> cloudfront.blogspot.com>>>>>>>>> On Sat, May 11, 2013 at 9:40 PM, Rahul Bhattacharjee <>>> [EMAIL PROTECTED]> wrote:>>>>>>> IMHO,I think the statement about NN with regard to block metadata is>>>> more like a general statement. Even if you put lots of small files of>>>> combined size 10 TB , you need to have a capable NN.>>>>>>>> can disct cp be used to copy local - to - hdfs ?>>>>>>>> Thanks,>>>> Rahul>>>>>>>>>>>> On Sat, May 11, 2013 at 9:35 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:>>>>>>>>> absolutely rite Mohammad>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:33 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>>>>>> Sorry for barging in guys. I think Nitin is talking about this :>>>>>>>>>>>> Every file and block in HDFS is treated as an object and for each>>>>>> object around 200B of metadata get created. So the NN should be powerful>>>>>> enough to handle that much metadata, since it is going to be in-memory.>>>>>> Actually memory is the most important metric when it comes to NN.>>>>>>>>>>>> Am I correct @Nitin?>>>>>>>>>>>> @Thoihen : As Nitin has said, when you talk about that much data you>>>>>> don't actually just do a "put". You could use something like "distcp" for>>>>>> parallel copying. A better approach would be to use a data aggregation tool>>>>>> like Flume or Chukwa, as Nitin has already pointed. Facebook uses their own>>>>>> data aggregation tool, called Scribe for this purpose.>>>>>>>>>>>> Warm Regards,>>>>>> Tariq>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:20 PM, Nitin Pawar <[EMAIL PROTECTED]>>>>>> > wrote:>>>>>>>>>>>>> NN would still be in picture because it will be writing a lot of>>>>>>> meta data for each individual file. so you will need a NN capable enough>>>>>>> which can store the metadata for your entire dataset. Data will never go to>>>>>>> NN but lot of metadata about data will be on NN so its always good idea to>>>>>>> have a strong NN.>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:11 PM, Rahul Bhattacharjee <>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>> @Nitin , parallel dfs to write to hdfs is great , but could not>>>>>>>> understand the meaning of capable NN. As I know , the NN would not be a>>>>>>>> part of the actual data write pipeline , means that the data would not>>>>>>>> travel through the NN , the dfs would contact the NN from time to time to>>>>>>>> get locations of DN as where to store the data blocks.>>>>>>>>>>>>>>>> Thanks,>>>>>>>> Rahul>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 4:54 PM, Nitin Pawar <>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>> is it safe? .. there is no direct answer yes or no>>>>>>>>>>>>>>>>>> when you say , you have files worth 10TB files and you want to>>>>>>>>> upload to HDFS, several factors come into picture>>>>>>>>>>>>>>>>>> 1) Is the machine in the same network as your hadoop cluster?>>>>>>>>> 2) If there guarantee that network will not go down?>>>>>>>>>>>>>>>>>> and Most importantly I assume that you have a capable hadoop>>>>>>>>> cluster. By that I mean you have a capable namenode.>>>>>>>>>>>>>>>>>> I would definitely not write files sequentially in HDFS. I would>>>>>>>>> prefer to write files in parallel to hdfs to utilize the DFS write features

> @Tariq can you point me to some resource which shows how distcp is used to> upload files from local to hdfs.>> isn't distcp a MR job ? wouldn't it need the data to be already present in> the hadoop's fs?>> Rahul>>> On Sat, May 11, 2013 at 10:52 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>> You'r welcome :)>>>> Warm Regards,>> Tariq>> cloudfront.blogspot.com>>>>>> On Sat, May 11, 2013 at 10:46 PM, Rahul Bhattacharjee <>> [EMAIL PROTECTED]> wrote:>>>>> Thanks Tariq!>>>>>>>>> On Sat, May 11, 2013 at 10:34 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>> @Rahul : Yes. distcp can do that.>>>>>>>> And, bigger the files lesser the metadata hence lesser memory>>>> consumption.>>>>>>>> Warm Regards,>>>> Tariq>>>> cloudfront.blogspot.com>>>>>>>>>>>> On Sat, May 11, 2013 at 9:40 PM, Rahul Bhattacharjee <>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>> IMHO,I think the statement about NN with regard to block metadata is>>>>> more like a general statement. Even if you put lots of small files of>>>>> combined size 10 TB , you need to have a capable NN.>>>>>>>>>> can disct cp be used to copy local - to - hdfs ?>>>>>>>>>> Thanks,>>>>> Rahul>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:35 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:>>>>>>>>>>> absolutely rite Mohammad>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:33 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>>>>>>>> Sorry for barging in guys. I think Nitin is talking about this :>>>>>>>>>>>>>> Every file and block in HDFS is treated as an object and for each>>>>>>> object around 200B of metadata get created. So the NN should be powerful>>>>>>> enough to handle that much metadata, since it is going to be in-memory.>>>>>>> Actually memory is the most important metric when it comes to NN.>>>>>>>>>>>>>> Am I correct @Nitin?>>>>>>>>>>>>>> @Thoihen : As Nitin has said, when you talk about that much data you>>>>>>> don't actually just do a "put". You could use something like "distcp" for>>>>>>> parallel copying. A better approach would be to use a data aggregation tool>>>>>>> like Flume or Chukwa, as Nitin has already pointed. Facebook uses their own>>>>>>> data aggregation tool, called Scribe for this purpose.>>>>>>>>>>>>>> Warm Regards,>>>>>>> Tariq>>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:20 PM, Nitin Pawar <>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>> NN would still be in picture because it will be writing a lot of>>>>>>>> meta data for each individual file. so you will need a NN capable enough>>>>>>>> which can store the metadata for your entire dataset. Data will never go to>>>>>>>> NN but lot of metadata about data will be on NN so its always good idea to>>>>>>>> have a strong NN.>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:11 PM, Rahul Bhattacharjee <>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>> @Nitin , parallel dfs to write to hdfs is great , but could not>>>>>>>>> understand the meaning of capable NN. As I know , the NN would not be a>>>>>>>>> part of the actual data write pipeline , means that the data would not>>>>>>>>> travel through the NN , the dfs would contact the NN from time to time to>>>>>>>>> get locations of DN as where to store the data blocks.>>>>>>>>>>>>>>>>>> Thanks,>>>>>>>>> Rahul>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 4:54 PM, Nitin Pawar <>>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>>>> is it safe? .. there is no direct answer yes or no>>>>>>>>>>>>>>>>>>>> when you say , you have files worth 10TB files and you want to>>>>>>>>>> upload to HDFS, several factors come into picture>>>>>>>>>>>>>>>>>>>> 1) Is the machine in the same network as your hadoop cluster?Nitin Pawar

> Thanks to both of you!>> Rahul>>> On Sun, May 12, 2013 at 5:36 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:>>> you can do that using file:///>>>> example:>>>> hadoop distcp hdfs://localhost:8020/somefile file:///Users/myhome/Desktop/>>>>>>>>>>>>>>>> On Sun, May 12, 2013 at 5:23 PM, Rahul Bhattacharjee <>> [EMAIL PROTECTED]> wrote:>>>>> @Tariq can you point me to some resource which shows how distcp is used>>> to upload files from local to hdfs.>>>>>> isn't distcp a MR job ? wouldn't it need the data to be already present>>> in the hadoop's fs?>>>>>> Rahul>>>>>>>>> On Sat, May 11, 2013 at 10:52 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>> You'r welcome :)>>>>>>>> Warm Regards,>>>> Tariq>>>> cloudfront.blogspot.com>>>>>>>>>>>> On Sat, May 11, 2013 at 10:46 PM, Rahul Bhattacharjee <>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>> Thanks Tariq!>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:34 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>>>>>> @Rahul : Yes. distcp can do that.>>>>>>>>>>>> And, bigger the files lesser the metadata hence lesser memory>>>>>> consumption.>>>>>>>>>>>> Warm Regards,>>>>>> Tariq>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:40 PM, Rahul Bhattacharjee <>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>> IMHO,I think the statement about NN with regard to block metadata is>>>>>>> more like a general statement. Even if you put lots of small files of>>>>>>> combined size 10 TB , you need to have a capable NN.>>>>>>>>>>>>>> can disct cp be used to copy local - to - hdfs ?>>>>>>>>>>>>>> Thanks,>>>>>>> Rahul>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:35 PM, Nitin Pawar <>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>> absolutely rite Mohammad>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:33 PM, Mohammad Tariq <[EMAIL PROTECTED]>>>>>>>> > wrote:>>>>>>>>>>>>>>>>> Sorry for barging in guys. I think Nitin is talking about this :>>>>>>>>>>>>>>>>>> Every file and block in HDFS is treated as an object and for each>>>>>>>>> object around 200B of metadata get created. So the NN should be powerful>>>>>>>>> enough to handle that much metadata, since it is going to be in-memory.>>>>>>>>> Actually memory is the most important metric when it comes to NN.>>>>>>>>>>>>>>>>>> Am I correct @Nitin?>>>>>>>>>>>>>>>>>> @Thoihen : As Nitin has said, when you talk about that much data>>>>>>>>> you don't actually just do a "put". You could use something like "distcp">>>>>>>>> for parallel copying. A better approach would be to use a data aggregation>>>>>>>>> tool like Flume or Chukwa, as Nitin has already pointed. Facebook uses>>>>>>>>> their own data aggregation tool, called Scribe for this purpose.>>>>>>>>>>>>>>>>>> Warm Regards,>>>>>>>>> Tariq>>>>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:20 PM, Nitin Pawar <>>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>>>> NN would still be in picture because it will be writing a lot of>>>>>>>>>> meta data for each individual file. so you will need a NN capable enough>>>>>>>>>> which can store the metadata for your entire dataset. Data will never go to>>>>>>>>>> NN but lot of metadata about data will be on NN so its always good idea to>>>>>>>>>> have a strong NN.>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:11 PM, Rahul Bhattacharjee <>>>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>>>>>> @Nitin , parallel dfs to write to hdfs is great , but could not>>>>>>>>>>> understand the meaning of capable NN. As I know , the NN would not be a>>>>>>>>>>> part of the actual data write pipeline , means that the data would not>>>>>>>>>>> travel through the NN , the dfs would contact the NN from time to time to

Yes , it's a MR job under the hood . my question was that you wrote thatusing distcp you loose the benefits of parallel processing of Hadoop. Ithink the MR job of distcp divides files into individual map tasks based onthe total size of the transfer , so multiple mappers would still be spawnedif the size of transfer is huge and they would work in parallel.

> No. distcp is actually a mapreduce job under the hood.>> Warm Regards,> Tariq> cloudfront.blogspot.com>>> On Sun, May 12, 2013 at 6:00 PM, Rahul Bhattacharjee <> [EMAIL PROTECTED]> wrote:>>> Thanks to both of you!>>>> Rahul>>>>>> On Sun, May 12, 2013 at 5:36 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:>>>>> you can do that using file:///>>>>>> example:>>>>>>>>> hadoop distcp hdfs://localhost:8020/somefile file:///Users/myhome/Desktop/>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sun, May 12, 2013 at 5:23 PM, Rahul Bhattacharjee <>>> [EMAIL PROTECTED]> wrote:>>>>>>> @Tariq can you point me to some resource which shows how distcp is used>>>> to upload files from local to hdfs.>>>>>>>> isn't distcp a MR job ? wouldn't it need the data to be already present>>>> in the hadoop's fs?>>>>>>>> Rahul>>>>>>>>>>>> On Sat, May 11, 2013 at 10:52 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>>>> You'r welcome :)>>>>>>>>>> Warm Regards,>>>>> Tariq>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:46 PM, Rahul Bhattacharjee <>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>> Thanks Tariq!>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:34 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>>>>>>>> @Rahul : Yes. distcp can do that.>>>>>>>>>>>>>> And, bigger the files lesser the metadata hence lesser memory>>>>>>> consumption.>>>>>>>>>>>>>> Warm Regards,>>>>>>> Tariq>>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:40 PM, Rahul Bhattacharjee <>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>> IMHO,I think the statement about NN with regard to block metadata>>>>>>>> is more like a general statement. Even if you put lots of small files of>>>>>>>> combined size 10 TB , you need to have a capable NN.>>>>>>>>>>>>>>>> can disct cp be used to copy local - to - hdfs ?>>>>>>>>>>>>>>>> Thanks,>>>>>>>> Rahul>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:35 PM, Nitin Pawar <>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>> absolutely rite Mohammad>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:33 PM, Mohammad Tariq <>>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>>>> Sorry for barging in guys. I think Nitin is talking about this :>>>>>>>>>>>>>>>>>>>> Every file and block in HDFS is treated as an object and for each>>>>>>>>>> object around 200B of metadata get created. So the NN should be powerful>>>>>>>>>> enough to handle that much metadata, since it is going to be in-memory.>>>>>>>>>> Actually memory is the most important metric when it comes to NN.>>>>>>>>>>>>>>>>>>>> Am I correct @Nitin?>>>>>>>>>>>>>>>>>>>> @Thoihen : As Nitin has said, when you talk about that much data>>>>>>>>>> you don't actually just do a "put". You could use something like "distcp">>>>>>>>>> for parallel copying. A better approach would be to use a data aggregation>>>>>>>>>> tool like Flume or Chukwa, as Nitin has already pointed. Facebook uses>>>>>>>>>> their own data aggregation tool, called Scribe for this purpose.>>>>>>>>>>>>>>>>>>>> Warm Regards,>>>>>>>>>> Tariq>>>>>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:20 PM, Nitin Pawar <>>>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>>>>>> NN would still be in picture because it will be writing a lot of>>>>>>>>>>> meta data for each individual file. so you will need a NN capable enough>>>>>>>>>>> which can store the metadata for your entire dataset. Data will never go to

> Yes , it's a MR job under the hood . my question was that you wrote that> using distcp you loose the benefits of parallel processing of Hadoop. I> think the MR job of distcp divides files into individual map tasks based on> the total size of the transfer , so multiple mappers would still be spawned> if the size of transfer is huge and they would work in parallel.>> Correct me if there is anything wrong!>> Thanks,> Rahul>>> On Sun, May 12, 2013 at 6:07 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>> No. distcp is actually a mapreduce job under the hood.>>>> Warm Regards,>> Tariq>> cloudfront.blogspot.com>>>>>> On Sun, May 12, 2013 at 6:00 PM, Rahul Bhattacharjee <>> [EMAIL PROTECTED]> wrote:>>>>> Thanks to both of you!>>>>>> Rahul>>>>>>>>> On Sun, May 12, 2013 at 5:36 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:>>>>>>> you can do that using file:///>>>>>>>> example:>>>>>>>> hadoop distcp hdfs://localhost:8020/somefile file:///Users/myhome/Desktop/>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sun, May 12, 2013 at 5:23 PM, Rahul Bhattacharjee <>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>> @Tariq can you point me to some resource which shows how distcp is>>>>> used to upload files from local to hdfs.>>>>>>>>>> isn't distcp a MR job ? wouldn't it need the data to be already>>>>> present in the hadoop's fs?>>>>>>>>>> Rahul>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:52 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>>>>>> You'r welcome :)>>>>>>>>>>>> Warm Regards,>>>>>> Tariq>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:46 PM, Rahul Bhattacharjee <>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>> Thanks Tariq!>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:34 PM, Mohammad Tariq <[EMAIL PROTECTED]>>>>>>> > wrote:>>>>>>>>>>>>>>> @Rahul : Yes. distcp can do that.>>>>>>>>>>>>>>>> And, bigger the files lesser the metadata hence lesser memory>>>>>>>> consumption.>>>>>>>>>>>>>>>> Warm Regards,>>>>>>>> Tariq>>>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:40 PM, Rahul Bhattacharjee <>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>> IMHO,I think the statement about NN with regard to block metadata>>>>>>>>> is more like a general statement. Even if you put lots of small files of>>>>>>>>> combined size 10 TB , you need to have a capable NN.>>>>>>>>>>>>>>>>>> can disct cp be used to copy local - to - hdfs ?>>>>>>>>>>>>>>>>>> Thanks,>>>>>>>>> Rahul>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:35 PM, Nitin Pawar <>>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>>>> absolutely rite Mohammad>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:33 PM, Mohammad Tariq <>>>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>>>>>> Sorry for barging in guys. I think Nitin is talking about this :>>>>>>>>>>>>>>>>>>>>>> Every file and block in HDFS is treated as an object and for>>>>>>>>>>> each object around 200B of metadata get created. So the NN should be>>>>>>>>>>> powerful enough to handle that much metadata, since it is going to be>>>>>>>>>>> in-memory. Actually memory is the most important metric when it comes to>>>>>>>>>>> NN.>>>>>>>>>>>>>>>>>>>>>> Am I correct @Nitin?>>>>>>>>>>>>>>>>>>>>>> @Thoihen : As Nitin has said, when you talk about that much data>>>>>>>>>>> you don't actually just do a "put". You could use something like "distcp">>>>>>>>>>> for parallel copying. A better approach would be to use a data aggregation>>>>>>>>>>> tool like Flume or Chukwa, as Nitin has already pointed. Facebook uses

It is being read sequentially but is it not potentially being written on multiple drives and since reading is typically faster than writing don't you still get a little benefit of parallelism?

On 5/12/2013 8:55 AM, Mohammad Tariq wrote:> I had said that if you use distcp to copy data *from localFS to HDFS* > then you won't be able to exploit parallelism as entire file is > present on a single machine. So no multiple TTs.>> Please comment if you think I am wring somewhere.>> Warm Regards,> Tariq> cloudfront.blogspot.com <http://cloudfront.blogspot.com>>>> On Sun, May 12, 2013 at 6:15 PM, Rahul Bhattacharjee > <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote:>> Yes , it's a MR job under the hood . my question was that you> wrote that using distcp you loose the benefits of parallel> processing of Hadoop. I think the MR job of distcp divides files> into individual map tasks based on the total size of the transfer> , so multiple mappers would still be spawned if the size of> transfer is huge and they would work in parallel.>> Correct me if there is anything wrong!>> Thanks,> Rahul>>> On Sun, May 12, 2013 at 6:07 PM, Mohammad Tariq> <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote:>> No. distcp is actually a mapreduce job under the hood.>> Warm Regards,> Tariq> cloudfront.blogspot.com <http://cloudfront.blogspot.com>>>> On Sun, May 12, 2013 at 6:00 PM, Rahul Bhattacharjee> <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote:>> Thanks to both of you!>> Rahul>>> On Sun, May 12, 2013 at 5:36 PM, Nitin Pawar> <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>> wrote:>> you can do that using file:///>> example:>> |hadoop distcp hdfs://localhost:8020/somefile file:///Users/myhome/Desktop/>>>>>>>>>>>>> |>>>> On Sun, May 12, 2013 at 5:23 PM, Rahul Bhattacharjee> <[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]>> wrote:>> @Tariq can you point me to some resource which> shows how distcp is used to upload files from> local to hdfs.>> isn't distcp a MR job ? wouldn't it need the data> to be already present in the hadoop's fs?>> Rahul>>> On Sat, May 11, 2013 at 10:52 PM, Mohammad Tariq> <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>> wrote:>> You'r welcome :)>> Warm Regards,> Tariq> cloudfront.blogspot.com> <http://cloudfront.blogspot.com>>>> On Sat, May 11, 2013 at 10:46 PM, Rahul> Bhattacharjee <[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]>> wrote:>> Thanks Tariq!>>> On Sat, May 11, 2013 at 10:34 PM, Mohammad> Tariq <[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]>> wrote:>> @Rahul : Yes. distcp can do that.>> And, bigger the files lesser the> metadata hence lesser memory consumption.>> Warm Regards,> Tariq> cloudfront.blogspot.com> <http://cloudfront.blogspot.com>>>> On Sat, May 11, 2013 at 9:40 PM, Rahul> Bhattacharjee <[EMAIL PROTECTED]

Using distcp to upload local file to hdfs might not work if launched from agateway host.Gateway hosts typically configured to only submit jobs and areonly aware of NN and JT, so mappers running in various data nodes might nothave access to the local fs of data node.

distcp is possible when data is loaded into the local fs of any of thedatanodes and then distcp is run from there.

> It is being read sequentially but is it not potentially being written on> multiple drives and since reading is typically faster than writing don't> you still get a little benefit of parallelism?>>> On 5/12/2013 8:55 AM, Mohammad Tariq wrote:>> I had said that if you use distcp to copy data *from localFS to HDFS*then you won't be able to exploit parallelism as entire file is present on> a single machine. So no multiple TTs.>> Please comment if you think I am wring somewhere.>> Warm Regards,> Tariq> cloudfront.blogspot.com>>> On Sun, May 12, 2013 at 6:15 PM, Rahul Bhattacharjee <> [EMAIL PROTECTED]> wrote:>>> Yes , it's a MR job under the hood . my question was that you wrote>> that using distcp you loose the benefits of parallel processing of Hadoop.>> I think the MR job of distcp divides files into individual map tasks based>> on the total size of the transfer , so multiple mappers would still be>> spawned if the size of transfer is huge and they would work in parallel.>>>> Correct me if there is anything wrong!>>>> Thanks,>> Rahul>>>>>> On Sun, May 12, 2013 at 6:07 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>> No. distcp is actually a mapreduce job under the hood.>>>>>> Warm Regards,>>> Tariq>>> cloudfront.blogspot.com>>>>>>>>> On Sun, May 12, 2013 at 6:00 PM, Rahul Bhattacharjee <>>> [EMAIL PROTECTED]> wrote:>>>>>>> Thanks to both of you!>>>>>>>> Rahul>>>>>>>>>>>> On Sun, May 12, 2013 at 5:36 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:>>>>>>>>> you can do that using file:///>>>>>>>>>> example:>>>>>>>>>> hadoop distcp hdfs://localhost:8020/somefile file:///Users/myhome/Desktop/>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sun, May 12, 2013 at 5:23 PM, Rahul Bhattacharjee <>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>> @Tariq can you point me to some resource which shows how distcp is>>>>>> used to upload files from local to hdfs.>>>>>>>>>>>> isn't distcp a MR job ? wouldn't it need the data to be already>>>>>> present in the hadoop's fs?>>>>>>>>>>>> Rahul>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:52 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:>>>>>>>>>>>>> You'r welcome :)>>>>>>>>>>>>>> Warm Regards,>>>>>>> Tariq>>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:46 PM, Rahul Bhattacharjee <>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>> Thanks Tariq!>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 10:34 PM, Mohammad Tariq <>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>> @Rahul : Yes. distcp can do that.>>>>>>>>>>>>>>>>>> And, bigger the files lesser the metadata hence lesser memory>>>>>>>>> consumption.>>>>>>>>>>>>>>>>>> Warm Regards,>>>>>>>>> Tariq>>>>>>>>> cloudfront.blogspot.com>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:40 PM, Rahul Bhattacharjee <>>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>>>> IMHO,I think the statement about NN with regard to block>>>>>>>>>> metadata is more like a general statement. Even if you put lots of small>>>>>>>>>> files of combined size 10 TB , you need to have a capable NN.>>>>>>>>>>>>>>>>>>>> can disct cp be used to copy local - to - hdfs ?>>>>>>>>>>>>>>>>>>>> Thanks,>>>>>>>>>> Rahul>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Sat, May 11, 2013 at 9:35 PM, Nitin Pawar <>>>>>>>>>> [EMAIL PROTECTED]> wrote:>>>>>>>>>>>>>>>>>>>

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Rahul Bhattacharjee 2013-05-16, 14:18

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